The invention relates to a dilator for the insertion of medical endoscopes for performing operations or examinations with a supporting probe on whose end is arranged a ball onto which can be shoved a plurality of dilation tubes having successively larger diameters.
Endoscopes are inserted into body cavities by means of sharp trocars with a trocar cannula, the trocar being removed after the sharp insertion for the purpose of introducing the endoscope through the trocar cannula. The said cannula can have a device for increasing the friction resistance against axial displacement such as a strip-like material of limited wall thickness applied spirally to the trocar cannula and also fixed to it. This significantly reduces frictional resistance on inserting and removing the trocar cannula without the diameter of the latter having to be very large, such a construction is shown in German Patent No. 2,218,901.
However, an operation by means of a trocar obviously represents a considerable risk and produces a large residual scar, because from the outset the sharp trocar tip produces a correspondingly large wound.
It has therefore long been standard practice to carry out dilation by means of a dilator of the aforementioned type, and it is then usual under X-ray examination to insert the probe with a ball on its tip into the kidney region, as an example. The probe can be very thin and can therefore be much moe easily introduced than the trocar tip. When the probe has reached the desired point in the human body, then according to the prior art successively a plurality of dilation tubes with an increasing diameter are advanced on the probe up to the ball. However, the procedure has always hitherto been such that before inserting a next tube with somewhat larger diameter, the preceding tube is completely removed from the cavity and from the probe. However, this leads to the opening becoming constricted somewhat again, so that the desired expansion action is partly cancelled out. This is among other things due to the fact that after removing a certain size tube, for example when operating on the esophagus, the latter shrinks again in the vicinity of a stenosis, which must be additionally expanded with the next dilation tube size.